Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
  • C22B26/10—Obtaining alkali metals
  • C22B26/12—Obtaining lithium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/005—Preliminary treatment of scrap
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/04—Obtaining nickel or cobalt by wet processes
  • C22B23/0407—Leaching processes
  • C22B23/0415—Leaching processes with acids or salt solutions except ammonium salts solutions
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
  • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
  • C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/006—Wet processes
  • C22B7/007—Wet processes by acid leaching
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the present invention relates to the end-of-life treatment of energy storage devices based on lithium technology.
• the invention relates to a hydrometallurgical process for the treatment at the end of life of said energy storage devices, for the separation of their components and the recovery of the metals contained therein.
• lithium batteries have become the most used power supply system for portable electronics devices.
• EV electric engines
• HEV hybrid engines
• the automotive lithium cell market can reach revenues of about 30 billion dollars in 2022, equal to about half of the total volume of lithium batteries (about 60 billion dollars), with a 30% annual growth starting from 2016.
• portable devices about 2 billion smartphones, 250 million tablets and 400 million portable PCs are put on the market every 20 months, with numbers constantly growing. Almost 30% of all the world production of lithium (about 35000 tons) is currently used for the production of lithium batteries.
• Lithium-ion batteries are storage devices of an electrochemical form of energy, consisting of an anode, a separator and a cathode.
• the anode is generally constituted by elemental lithium reversibly intercalated in the interplanar spaces of the crystalline lattice of high crystallinity carbononium materials (for example graphite);
• the separator consists of a polymeric membrane (generally polypropylene or polyvinylidene difluoride, PVDF) permeable to lithium ions;
• the electrolyte consists of a lithium salt (generally lithium salts soluble in an organic environment such as, for example, LiBF 4 or LiPF 6 ) dissolved in an organic aprotic solvent, with a wide electrochemical stability window (such as diethylcarbonate), but also with non-negligible characteristics of volatility and flammability;
• the cathode is generally made up of oxides or insoluble salts of transition metals, capable of reversibly intercal
• BMS electronic management system
• the methods of securing lithium batteries at the end of their life can be grouped into three main categories: i) reduction of the residual charge 3 8 ; ii) heat treatments 13 15 and iii) mechanical treatments in controlled environments 9,10 .
• the discharge of the batteries can be obtained by various methods, in particular: i) by immersing the cells in a conductive electrolytic solution 3 6 ; ii) by manual discharge via a dedicated device 7,8 .
• the heat treatments can exploit the heat, to evaporate the flammable organic solvents, obtaining their removal, or otherwise they can use cryogenic liquids (such as liquid nitrogen) to drastically reduce their reactivity 13 15 .
• Thermal treatments for the removal of organic solvents present high costs, due to heating and, above all, they present the need to reduce the emissions of highly toxic gases, such as CO, HF and PF 5 , deriving from the decomposition of the polymeric separators and of the and binder 20, 21 .
• the heat treatment is not completely free of risks: in fact, it is possible to generate explosions, since the heating can lead to an increase in pressure inside the cells, in the event that the vent valve is faulty.
• cryogenic liquids presents, in addition to the high cost thereof, also safety problems for operators, such as the risk of asphyxiation and burns.
• Processes operating in a controlled environment employ appropriate gases, such as nitrogen or carbon dioxide, to deprive of oxygen the environment in which batteries are fragmented.
• gases such as nitrogen or carbon dioxide
• the first processes are affected by problems of operator safety and by a high cost of management, while the latter produce a large quantity of wastewater, to be treated appropriately, and introduce a further phase of separation of materials 9 12,16 .
• the methods of detachment of the collectors from the active materials have been classified and subdivided into thermal, physical or wet processes.
• the binder and the separating membrane are pyrolyzed in air or in an inert atmosphere, at temperatures in the range of 300 to 800 °C.
• This treatment degrades the binder, facilitating the detachment of active powder from metal collectors, preventing them from being compromised 3, 31 35 .
• This system has the disadvantage due to the production of toxic gases such as HF, CO and PF 5 , especially in the presence of traces of moisture. These gases require an adequate abatement system, which affects the costs of installation and processing.
• the internal components of the cells are put in contact, under mechanical or ultrasonic agitation, with a liquid agent, able to dissolve or weaken the action of the binder.
• Some methods include the use of organic solvents such as N-dimethyl formamide (DMF) 39 , N-methyl pyrrolidone (NMP) 40 43 , or other solvents 3,44,45 for the dissolution of the binder, assisted by stirring 3,39,41 , or ultrasounds 3,6,40 .
• DMF N-dimethyl formamide
• NMP N-methyl pyrrolidone
• the resulting material is mainly composed of the powders of the electrode materials and can be treated with metallurgical or hydrometallurgical methods.
• the exhausted cells are generally incinerated, with the aim of destroying plastics, solvents, separators and carbonaceous materials.
• the materials are generally recovered as molten metals 20,29,40 , or by the electrolysis of molten salts 3,11 ,23 .
• the hydrometallurgical methods provide for the dissolution (leaching) of metals and metal oxides in acid or alkaline solution.
• a reducing agent is often included, to facilitate the solubilization of metal oxides with high oxidation states (such as, for example, cobalt III oxides).
• Many methods use sulfuric or hydrochloric acid, in combination with a reducing compound, such as H 2 0 2 13, 17,22,30,35,50,60,61 citric acid 62 , sodium thiosulfate 59,63 or sugars 9 .
• metals can be separated by precipitation 6,9,12,17,24,27,31 ,38,49,54,55,57,58 , extraction in organic solvents 9,23,59 , electroreduction 13,31 , combinations of these techniques 5,9,13,55 or can be used to re-produce cathode materials for batteries 17,37,41 ,42,54,56,60 .
• the solution according to this invention aims to provide a process for the treatment of lithium batteries, designed to overcome the critical issues that plague the processes according to the prior art of recovery of metals contained therein.
• the method for treatment of lithium batteries and recovery of the metals contained therein comprises the following steps: completely discharging the single cells by immersion in a conductive solid material, so that the disassembly of the batteries can be conducted in safe conditions; removal of the active materials from metal collectors, non-destructive to the latter, by immersing the black mass in a solution of a weak organic acid; dissolving (by leaching or leaching) metals from active powder by using inorganic acids in combination with organic acids having reducing properties; separation of lithium from the other metals present in the liquor, by precipitation of the latter, by using sodium or potassium sulphide; recovery of lithium, by precipitation as carbonate.
• the object of the present invention is therefore to provide a hydro metallurgical process for the treatment of lithium batteries and the recovery of the metals contained, which allows to overcome the limits of the processes according to the prior art and to obtain the previously described technical results.
• a further object of the invention is that said hydrometallurgical process can be carried out with substantially contained costs.
• Not least object of the invention is to propose a hydrometallurgical process for the treatment of lithium batteries and recovery of the metals contained therein that is simple, safe and reliable.
• said solid electric conductor is composed of copper, bronze, brass, iron or steel, aluminum, carbon.
• said step of separating black mass from metal shells can be obtained by manual opening, grinding, cutting or fragmentation.
• said aqueous solution of a weak organic acid used in said step of removing active powder from metal collectors and from separating membranes is constituted by formic acid in a concentration range comprised between 0,5 and 8M in a concentration range comprised between 4:1 a 10:1 with respect to the black mass; preferably at a temperature comprised between 10 and 80 °C, with stirring, for a period comprised between 30 and 240 minutes.
• said step of leaching provides for the addition of chloridric acid, in such an amount to reach a concentration comprised between 3 and 6M in solution, preferably at boiling temperature, for a period not shorter than 30min.
• the pH of the solution can be adjusted within a range of 5 to 7 by the addition of a solution of an alkaline hydroxide in a concentration comprised between 10 and 30%, preferably operating at a temperature comprised between 20 and 80 °C.
• said step of acidification of the lithium solution with strong acids involves the pH change to a value lower than 2.
• said step of precipitation of lithium as carbonate is operated at a temperature comprised between 70 °C and the boiling temperature.
• the hydrometallurgical process for the treatment of lithium batteries and the recovery of the metals contained therein according to the present invention and the relative system provide a step of discharge of the cells by immersion in an electrically conductive solid, with the purpose of creating an electrical contact between the cell terminals.
• similar discharge processes according to the prior art such as for example Chinese patent application No.
• the hydro-metallurgical process according to the present invention does not require the use of a mixture of water and a conductive medium (coal, iron, copper), which on the one hand can make temperature control easier, but on the other hand would involve the problems related to the previously exposedl iquid discharge methods 4,17 19 , ie the electrolytic corrosion with sludge formation and possible development of toxic gases, and furthermore, it would be necessary to wash the cells after treatment, to guarantee the elimination of traces of the conductive medium and to prevent the contamination of the internal components of the batteries subjected to subsequent treatments.
• the procedure according to the present invention on the other hand, using only a solid dry conductive material, has the following advantages: i) lowering of the cell potential to values close to zero, an acceptable level to prevent the risks of explosion or fire, ii) absence of development of by products, and iii) absence of modifications of the conductive material, which is therefore reusable for numerous treatments.
• the process according to the present invention provides for the use of a weak organic acid with reducing properties, preferably formic acid, and consequently, compared to the methods present in literature, is able to overcome the problems related to the separation of dust-collectors for the following reasons: i) the corrosion of the collectors is extremely reduced, while maintaining the efficiency of the detachment process typical of treatments with more aggressive species 46 53 ; ii) the costs of the reagents are limited compared to processes using known organic solvents 3,39 45 ; iii) the reproducibility and the efficiency of the detachment process are high compared to dry methods 14,15,31 38 ; iv) there is no need for a further separation of the active material from the detachment solution (with regard to this last point, one of the greatest potentials of this step consists in the possibility of exploiting the organic acid both for the detachment of active powder, both for its reducing characteristics in the subsequent step of leaching of active metals).
• the etching formulation proposed in the process according to the present invention is composed of an organic acid with reducing characteristics, in combination with a strong inorganic acid, the process allowing the quantitative dissolution of all the metal species present in powder, with efficiencies comparable to acid etchings much more aggressive known in the prior art (for example aqua regia, HNO 3 /HCI in ratio 1 /3, H 2 0 2 /H 2 S0 4 ), leaving as the only insoluble residue the carbon used in formulation of the electrodes.
• the organic acid used in the step of detachment of the powders from the collectors described above is used as a reducing agent in this step of leaching.
• a plant for the execution of the hydrometallurgical process for the treatment of lithium batteries and the recovery of the metals contaimed therein comprises the following sections: a section for the complete discharge of the individual cells by immersion in a conductive solid material, so that the disassembly can be conducted in safe conditions; a section for the removal of active materials from metal collectors, non destructive for the latter, by immersing the black mass in a solution of a weak organic acid; a section for dissolving (leaching or leaching) metals from active powder by using inorganic acids in combination with organic acids having reducing properties; a section for the separation of lithium from the other metals present in the "liquor" by precipitation of the latter through the use of sodium or potassium sulphide; and a lithium recovery section by precipitation as carbonate.
• the hydrometallurgical process for the treatment of lithium batteries and the recovery of the metals contained therein provides that the batteries 1 reach a first station 2, where they are deprived of their control and protection circuits 3 (BMS), and are then sent to a discharge container 4 for discharge of the cells, wherein they are immersed in a solid electric conductor 5, i.e. a solid material, electrically and thermally conductive, for a minimum time equal to 2 hours, preferably between 24 and 48 hours.
• a solid electric conductor 5 i.e. a solid material, electrically and thermally conductive
• the cells after being discharged, are disassembled and ground in a grinding station 6. After grinding, the metal shells 7 can be removed by means of separation methods which are part of the prior art.
• the remaining material referred to as black mass 8, is mainly composed of active materials, supported on copper and aluminum collectors, and polymer separators.
• the black mass 8 is then subjected to the step of separation of the active electrode materials (coal plus active metals) from the metal collectors into a powder/collector separation reactor 9.
• the process involves the treatment of the black mass with a solution of a weak acid 10 , in particular a weak organic acid (formic acid), in a concentration in the range 0.5-8M and stirred for 30-240 minutes at a temperature between 10 and 80 °C and with a treatment solution/black mass ratio between 4:1 and 10:1 by weight.
• the optimal conditions identified for this step are: formic acid 3M, solution/black mass ratio of about 5:1 , one hour of stirring at 60 °C. This process is able to effectively remove the active materials from the copper and aluminum collectors, without appreciable dissolution of the latter.
• the humid mixture 1 1 of collectors and detached powders accumulates at the bottom of the separation reactor 9, from which it is sent to a sifter 1 1 , where collectors and polymer membranes 12 are separated from the mixture 13 of carbonaceous powders containing the active metals in the solution of formic acid.
• Collectors and polymeric membranes 1 1 are sent to a washing station 14, where they are subjected to washing with water 15, by which further amounts of carbonaceous particles containing active metals are separated, and then to a drying station 16, to be finally recovered.
• the mixture 13 is sent to an etching reactor 17, where it is subjected to leaching, or chemical etching, by adding water 18 and a mineral acid 19, preferably hydrochloric acid.
• a weak organic acid appropriately selected with reducing properties (for example formic acid)
• An amount of mineral acid is added to obtain a concentration between 3 and 6M, preferably 4M.
• the etching solution 20 is subjected to heating under stirring for 30-120 minutes, preferably boiling for 60 minutes.
• the obtained liquid liquor 21 is separated from the residues of insoluble carbon materials 22 by filtration in a filtering station 23.
• the insoluble phase 22 is mainly constituted by carbonaceous materials, which could possibly be recovered and used for other purposes.
• the liquid phase 21 contains ions of the metals present in the cathode material.
• the separation of lithium from the liquor or liquid phase 21 is obtained by precipitation in a precipitation reactor 24.
• the pH of the liquor 21 is brought to a value between 5 and 7, by adding an aqueous solution of an alkaline hydroxide, in concentration between 10 and 30% by weight, preferably 20% sodium hydroxide.
• a solution 25 of an alkaline sulfide is then added under stirring in a concentration of 1 to 3M, preferably 2M sodium sulfide, maintaining the temperature in a range of from 20 to 80 ° C.
• This solution 25 is added until the complete precipitation of all the transition metals present in the solution is obtained, with the exception of the lithium ions. This condition can be determined by methods according to the prior art.
• the suspension is digested for at least 30 minutes, to obtain a clarified solution 26 containing lithium and a precipitate 27.
• the precipitate 27, containing the metal sulfides, is separated by filtration in a station of filtering 28.
• lithium can be recovered by precipitation in the form of carbonate, as follows: the sodium and/or potassium content of the solution is reduced due to the effect of pH and concentration.
• the clarified solution 26 can be acidified, preferably with hydrochloric acid 29, to a pH lower than 2, concentrated by evaporation in a special evaporation tank 30, obtaining the precipitation of the sodium and potassium salts 31 from the solution 32 of lithium and sodium or potassium, which are separated by filtration into a filtering station 33.
• the lithium is finally obtained as carbonate, by hot precipitation in a precipitation reactor 34, following the addition of a solution 35 of sodium or potassium carbonate.
• the lithium carbonate 36 precipitates at the bottom of the precipitation reactor 34, is separated, by filtration in a filtering station 37, from the mother liquors 38, which can be recycled in the step of precipitation.
• the lithium carbonate 36 is then purified by recrystallization.
• the cells were then separated from the filings by sieves and manually disassembled using a circular saw for the removal of plastic and steel hulls. No flames, heat or gas development were detected during this procedure.
• the internal parts of the cells composed of anode, cathode and polymeric separators, were cut manually into fragments of about 10mm on each side.
• the fragments, weighing 106.4g, were placed in a beaker, added with 530ml_ of a 3M solution of formic acid and heated under stirring for one hour at 60 °C, obtaining the detachment of the active materials from the metal collectors.
• the separation of the suspended powders in solution containing the active metals was obtained through a sieve of appropriate dimensions; the metal collectors of copper and aluminum and the polypropylene separators were then washed, dried and finally weighed.
• the weight of this fraction was 34.9g; no evident corrosion was detected on the copper foils, while the surface of the aluminum foils was opaque, thus indicating partial corrosion.
• the suspension consisting of the active powder and the formic acid solution was then inserted into an etching reactor for the step of dissolution (leaching) and 500ml_ of concentrated hydrochloric acid (37% by weight) were added and heated up to boiling for un hour under stirring. After this time, the solution was allowed to cool and filtered, separating the insoluble solids in the reaction environment.
• the solid part, made up entirely of elemental carbon, was dried and weighed, amounting to about 23.8g (about 20% of the weight of the entire black mass).
• the solution containing the ions of the active metals had a volume of about 1 l OOrmL of volume and was analyzed by ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) to determine the content of metal ions, the results of which are shown in Table 1.
• Table 1 metal content, expressed in ppm and in% by weight, of the liquor corresponding to the batch treated in Example 1 )
• the copper amount is very low, indicating a slight dissolution during the step of detachment of the powders from the collectors, while a not negligible quantity of aluminum in solution has been detected.
• the“liquor” was heated up to 60 °C, the pH increased up to a value of around 5 by means of an aqueous solution of 20% by weight sodium hydroxide (about 190g of equivalent NaOH) and a 2M Na2S solution was added for the precipitation of all metal ions with the exception of lithium. About 220ml_ of 2M sodium sulfide solution was needed. The precipitate was then filtered, dried and weighed; about 41.2g of transition metal sulfide were obtained.
• the aqueous portion, having a volume of 2.2L, containing lithium and sodium ions was acidified to pH 1 with hydrochloric acid and evaporated to about 1/20 of its initial volume, thus obtaining the precipitation of sodium chloride, which was then separated from the mother liquor by filtration and removed.
• the supernatant, enriched with lithium chloride was heated up to 90 °C, obtaining, by adding 60ml_ of 40% aqueous potassium carbonate, the precipitation of lithium carbonate, then separated from the mother liquors by filtration .
• the obtained precipitate washed with water at boiling temperature and subsequently dried and weighed, amounted to about 13.87g, corresponding to 84% of the lithium contained in the etching liquor.
• the obtained product was analyzed by ICP-MS. The results are shown in Table 2.
• the thermal energy released by the discharge process amounted to about 6kJ.
• the cells were then separated from the filings by sieves and manually disassembled using a circular saw for the removal of plastic and steel hulls. No flames, heat or gas development were detected during this process.
• the internal parts of the cells, composed of anode, cathode and separators, were cut manually into 10mm diameter fragments and left for two hours exposed to an air stream in order to eliminate the organic solvents that make up the electrolyte before proceeding with other treatments.
• the copper and aluminum metal collectors and the polypropylene separators were separated by a sieve, washed, dried and finally weighed.
• the weight of this fraction was 127.5g; partial corrosion was detected on the copper foils, while the thickness of the aluminum foils was appreciably reduced, thus indicating substantial corrosion.
• part of the active powder remained adhered to the surface of the aluminum.
• the suspension consisting of active powder and the formic acid solution was then inserted into the leaching reactor and added with 1 3L of concentrated hydrochloric acid (37% by weight) and reflow heated for one hour under stirring.
• phase composed of metal collectors and separators was etched in aqua regia and also analyzed by ICP-MS, with the aim of determining the metallic content; the values are shown in table 4, while the percentage distribution between the two phases, powders and foils, are shown in table 5.
• the metals contained in the liquor were precipitated by adding a 2M solution of Na2S at 60 °C under stirring until the reaction was complete (further addition of sulfide did not lead to any additional formation of precipitate). About 780ml_ of 2M sodium sulfide solution was needed. The precipitate was then filtered, dried and weighed; approximately 144.8g of transition metal sulfide were obtained. The aqueous part, having a volume of about 8.0L, containing lithium and sodium ions was acidified to pH 1 with hydrochloric acid and evaporated to about 1/20 of its initial volume, thus obtaining the precipitation of sodium chloride, which was then separated from the mother liquors by filtration and removed.
• the supernatant, enriched with lithium chloride, was heated up to 90 °C, obtaining, by adding 200ml_ of 40% aqueous potassium carbonate, the precipitation of lithium carbonate, then separated from the mother liquors by filtration.
• the obtained precipitate washed with water at boiling temperature and subsequently dried and weighed, amounted to about 50.2g, corresponding to 83.7% of the lithium contained in the etching liquor and to about 71.7% of the content total of lithium contained in the lot.
• the obtained product was analyzed by ICP-MS. The results are shown in table 6.
• the thermal energy released by the discharge process amounted to about 12kJ.
• the cells were then separated from the filings by means of sieves and manually disassembled, using a circular saw for the removal of plastic and steel hulls, whose weight amounted to 71.3g. No flames, heat or gas development were detected during this procedure.
• the internal parts of the cells composed of anode, cathode and separators, were cut manually into 10mm diameter fragments and left for two hours exposed to an air stream in order to eliminate the organic solvents that make up the electrolyte before proceeding further.
• the fragments weighing 281.3g were placed in a beaker, added with 1 4L of a solution of 3M formic acid, and stirred for one hour at room temperature, obtaining the detachment of the active materials from the metal collectors.
• the copper and aluminum metal collectors and the polypropylene separators were separated by a sieve, washed, dried and finally weighed.
• the weight of this fraction was 94.3g; no evident corrosion was detected on the copper foils, while the surface of the aluminum foils was opaque, thus indicating a possible partial corrosion.
• Part of the powders had remained attached to the surface of the aluminum and separators.
• the suspension consisting of the active powder and the formic acid solution was then inserted into the leaching reactor and added with 900 ml_ of concentrated hydrochloric acid (37% by weight) and reflow heated for one hour under stirring. After this time, the solution was allowed to cool and filtered, separating the insoluble solids from the reaction environment.
• the solid part consisting entirely of elemental carbon, was washed with 250ml_ of water, dried and weighed, amounting to about 54.9g (about 20% of the weight of the entire black mass).
• The“etching liquor” (about 3L of volume) was analyzed by ICP-MS to determine the metallic content; the data are shown in table 7.
• phase composed of metal collectors and separators was etched in aqua regia and also analyzed by ICP-MS, in order to determine its metallic content; the values are shown in Table 8, while the percentage distribution between the two phases, powders and foils, are shown in
• Tabella 8 metal content (expressed as % by weight) in the etching solution of the collectors of Example 3)
• the copper was not appreciably etched during the step of separation of the powders, while a not negligible quantity of aluminum in solution was detected. It should be noted, however, that part of the active powder remained attached to the aluminum foils (Table 8).
• the pH of the “liquor” was adjusted around a value of 5 by adding an aqueous solution of 20% by weight sodium hydroxide (about 500g of equivalent NaOH) leading to the precipitation of the traces of aluminum as hydroxides, which were eliminated by filtration.
• the metals contained in the liquor (with the exception of lithium) were precipitated by adding a solution of Na2S 2M at 60 °C under stirring until the reaction was complete (further addition of sulfide did not lead to further precipitate formation).
• the obtained precipitate washed with water at boiling temperature and subsequently dried and weighed, amounted to about 39.7g, corresponding to 84.1 % of the lithium contained in the etching "liquor" and to approximately 74.6% of the total content of lithium contained in the batch.
• the obtained product was analyzed by ICP-MS. The results are shown in table 10.
• EP21 13138B1 h) CA2678545A1 ; i) CA2678545C; j) JP4406845B2; k) W02008102240A1 ; I) CN101617435A; m) JP2008204755A

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